Aromatic-alkene copolymers of less than 5 per cent aromatic content



Patented Oct. 20, 1953 AROMATIC-ALKENE COTOLYMERS OF LESS- THAN 5 PERCENT AROMATIC CONTENT William J. Sparks, Westfield, and David W. Young,Roselle, N. J., assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application July 27, 1950, SerialNo. 176,256

10 Claims. (01. 260--88.1)

This invention relates to novel high molecular weight polymeric chemicalproducts and to methods of making same. More particularly, it relates tothe preparation of copolymers consisting almost entirely of aliphaticconstituents but containing avery small amount of a combined cyclicmodifying constituent. The invention may be typified by a copolymer of97% of isobutylene and 3% of styrene.

U. S. Patents 2,213,423 and 2,274,749 disclose copolymers of isobutyleneand styrene in a general way, and describe methods of effecting thecopolymerization, i. e. at temperatures below 0., e. g. l0 C., 40 C., 80C., or lower, and by the use of an active halide polymerizationcatalyst. These patents disclose that the proportions of the tworeactants may be varied in order to produce thermoplastic copolymershaving the desired hardness, melting point, plasticity, etc., and

that the proportion of olefin used, e. g. isobutylene, may range from 1to 90%, the balance of 10-99% by weight being styrene or equivalentpolymerizable cyclic compound. However, it is difficult or impossible toprepare such copolymers in a very high molecular weight range such as50,000, 100,000 or above, and another difiiculty is that when any suchcopolymers having molecular weights even as low as 10,000 are dissolvedin parafiinic lubricating oils they tend to come out of solution whencooled down to temperatures of about 50 F. or lower. Furthermore,although when compounded with natural or synthetic rubber, suchcopolymers greatly improve the workability thereof, they generallyeffect a slight reduction either in tensile strength or in elongation.

It is also known that isobutylene alone can be polymerized to polymersranging from viscous sticky fluids having a molecular weight range of1,000 to 10,000 or 15,000, on up through a tacky plastic stage, to drysubstantially non-tacky rubbery polymers having molecular weights of150,000 and even much higher. However, such polybutenes, particularlythose of very high molecular weights, do not have as good stability tosunlight and ultraviolet light as might be desired, and do not haveentirely satisfactory stability against thermal or mechanical molecularweight breakdown.

It has now been found that between the pure polybutenes and thestyrene-isobutylene copoly- .mers having 5 or or more per cent ofcombined styrene, it is possible to make novel copolymers having noveland unexpected characteristics not possessed by either of the twopreviously -known types of polymeric materials. Thus, it

is found that when about 0.5 or 1% up to about 4 or 4.5% or so ofstyrene is copolymerized with isobutylene, the resultant copolymers havesurprisingly better thermal stability than polybutene, and it isbelieved that the small amount of styrene combined in the copolymermolecule acts somewhat like an anti-oxidant in preventingdepolymerization or molecular weight breakdown at elevated temperature,which is thought to be at least partly due to or at least accelerated byincipient oxidation, because known oxidation inhibitors such as certainalkyl phenols tend to reduce the thermal decomposition of highmolecul-ar weight polybutenes.

These new copolymers may be milled into .natural rubber or syntheticrubbers such as GR-S (buta-diene-styrene), GR-A (butadiene-Tacrylonitrile), and GR,I (isobutylene-isoprene copolymer of lowunsaturation), as well as other types such as neoprene, and organicpolysulfide rubbers, at hot mill temperatures such as ISO-330 1R, withless undesirable breakdown than can sulting copolymers will have amolecular weight 1 (by the Staudinger method) of at least r 30,000 andpreferably at least 50,000. With previously used high percentages ofstyrene in the copolymer it has been diflicult or impossible to obtainproducts having molecular weights higher than about 30,000 or 40,000.For instance, if a mixture of 40% of styrene and of isobutylene iscopolymerized at 103' C'. in methylchloride solution and using ascatalyst a solution of aluminum chloride dissolved in methyl chloride,the resulting copolymer will have a molecular weight of about 25,000,and if the proportion of reactants is reversed so as to use 60% ofstyrene in the feed, the copolymer will have only 18,000 to 20,000 mol.wt., whereas under similar copolymerization conditions copolymers havingless than of combined styrene are made having molecular weights rangingfrom about 70,000 up to 200,000. These new copolymers when made in thevery high molecular weight range such as 150,000 to 200,000 or higherare dry, rubbery products having no cold flow. They resemblepolybutenein generalphysical texture and appearance except that for any particularmolecular weight they have a physical texture corresponding more closelyto a polybutene having a molecular weight about higher.

Another remarkable characteristic :of these new copolymers is that theyhave unite gradual heat-softening characteristics much more resemblingpure polybutene .than themore sharply thermoplastic type of heatsoftening properties of styrene-isobutylene copolymers having largeramounts of combined styrene.

The copolymers of this invention ailsohaveran unexpectedly goodcombination of good solubility in paraffinic lubricating oils even atvery low temperatures, e. g. 0 F., and good stability under shear tests.An indication that the combined styrene content of these new copolymersis critically important even though small in quantity, is that thesecopolymers are found to dissolve in benzene to form a clear solution at20 C. whereas polybutenes of similar molecular weight do not. Anothercharacteristic which may be particularly valuable under certaincircumstances, is that the copolymers of this inventiongenera'lly have amuch narrower molecular weight spread than isobutylene polymers madeunder similar polymerization conditions -of temperature, type ofcatalyst and solvent.

In carrying out the copolymerization, the catalyst to be used may be"aluminum chloride,

AlBm LAIBraAlK-OCQHs) 3,

If desired, such catalyst may be dissolved in a solvent such as carbondisulfide, a low molecular weight sulfurfree saturated hydrocarbon, alower alkyl halide, e. g. methyl chloride or ethyl chloride or a mixtureof methyl chloride with butane or propane, at or below the boiling pointof the catalyst solvent, and then the catalyst solution cooled down, r

. BFs-isopropyl alcohol complex, BFa solution in ethylene, activated BFZcatalyst in ethylene solution.

The copolymerization is preferably carried out in the presence of avolatile solvent or diluent or refrigerant, such as propane, ethane,ethylene, methyl chloride, carbon dioxide (liquid or solid) etc.; suchmaterials may be used either as internal refrigerants or externalrefrigerants or both, to remove the liberated heat of polymerization.One advantage of the present invention is that due to the use of lessthan 5% of styrene or equivalent cyclic constituent, both the feedmaterials and resulting copolymers are sufficient- 1y soluble in loweraliphatic hydrocarbon solvents such as propane, that it is not necessaryto use a lower alkyl halide solvent such as methyl chloride as isrequired for copolymerizations, involving higher amounts of styrenereaction.

After completion of the copolymerization, residual catalyst may behydrolyzed by adding an alcohol, for example, isopropyl alcohol or ethylalcohol, or water or both, and removed by washing the product with waterand preferably also with dilute aqueous caustic soda. Any residualsolvent or wash water or other hydrolyzing agents may be removed byheating the copolymer with or without milling, kneading or otheragitation.

Instead of iso'butylenaasthe alkene, other lower aliphatic olefins maybe used, preferably isoolefins having 4 to 8 carbon atoms such asisopentene (methyl-2 butene-l), or a normal pen- -teneobtained bydehydration of secondary amyl alcohol, although other lower olefins suchas propylene may also be used.

Instead of styrene as the polymerizable olefinic cyclic compound, othermaterials may be used-such as "alpha-methyl styrene, para-methylstyrene, alp'ha-para-dimethyl styrene, dihydronaphthalene, indenes, etc.Various derivatives nriiomologues of such compounds having one or moreshort alkyl groups (e. g. 1 to 10 carbon atoms) attached to the cyclicnucleus and not interfering with the polymerization,.may be used.

The proportions to be used in making up the copolymerization feed stockmay vary somewhat according to the intended purpose. Usually, thepolymerizable mono-olefinic hydrocarbon containing a cyclic nucleus, e.g. styrene or equivalent material, should be used in a concentration orat least 0.01% but less than 5% by weight, preferably about 0.5% to"4.5% and better still for most purposes about 1.0 to 4.0%. Thealiphatic olefin such as isobutylene will constitute the remainder ofthe active'copolymerization feed and it will be present in aconcentration greater than and may be as great as 99.99%. It is foundthat even relatively minute amounts, much less than 1%, of styrene, whencop'lymerized with isobutylene, have a very beneficial effect instabilizing the polybutene chain against depolymerization due tosunlight, ultraviolet light, heat and oxidation.

The preferred procedure for carrying out the copolymerization of thisinvention is to mix the isobutylene and styrene, or their equivalents,cool them down to the desired operating temperature by either externalor internal refrigeration, preferably having some diluent or solventpresent, for instance in a proportion of about 1 to 5 vol umes ofsolvent per volume of mixed copolymerization feed, and then adding tothat reaction mixture the desired amount of catalyst or solutionthereof, preferably agitating the mixture well during the addition ofthe catalyst.

After hydrolysis and removal of catalyst as previously mentioned, theresultant high molecular weight copolymer may be heated if desired, withor without milling or other agitation, to remove residual traces ofsolvent, diluent or refrigerant or of water or alcohol left from theWashing step.

The copolymer per se is a plastic, and in most cases rubbery andelastic, solid having an average Staudinger molecular weight above30,000, and preferably above 50,000. Molecular weights well above300,000 have been obtained. Copolymers having a molecular weight below50,000 generally are somewhat tacky, while those in the vicinity of100,000 mol. wt. are only very slightly tacky and those in the vicinityof 150,000 or 200,000 are dry and free from cold flow. Generally,according to this invention, a substantially saturated copolymer isproduced, i. e. having less than about 0.1 iodine number and being sub-'5 stantially free from tendencies to absorb oxygen and harden due toaliphatic unsaturation.

The isobutylene-styrene type copolymer can be cured through the presenceof the benzene ring by reagents such as formaldehyde, or acetylperoxide, heptoyl peroxide, etc.

The copolymers of this invention may be used for a wide variety ofpurposes in addition to those mentioned above. For instance they may beused for coating metal, wood, paper, cloth, glass, and for laminatingvarious thin flexible sheet material such as paper cloth, metal foil,regenerated cellulose, cellulose acetate etc., and for such purposes thecopolymers may be dissolved in a volatile solvent such as naphtha, andapplied by various conventional methods such as dipping, spraying, rollcoating, etc., followed by evaporation of the solvent, or the copolymersmay be compounded with softening or plasticizing materials such asmineral oils, waxes, e. g. paraffin wax or petrolatum, asphalt orthermoplastic compatible resins preferably of the hydrocarbon type, andwhen thus softened or plasticized, may be used in molten orheat-softened condition for any of the purposes above-mentioned.

These products also are particularly well adapted for electricalinsulation purposes, particularly for dielectric medium, alone ortogether with parafiin wax, in electrical condensers.

These products may also be compounded with other types of high molecularweight polymeric materials, preferably those of predominate aliphaticnature such as polybutene, polyethylene and other polymerized olefins,as well as synthetic rubber of the GR-I type, e. g. made by lowtemperature Friedel-Crafts polymerization of isobutylene with about 1 to3% of isoprene, although they may also be compounded with natural rubberand other types of synthetic rubber such as those made by emulsionpolymerization of butadienealone or in together with a minor proportionof styrene or acrylonitrile.

The copolymers of this invention are miscible with molten paraffin waxin all proportions, and

therein differ greatly from styrene-isobutylene copolymers having ahigher styrene content, c. g. 10 to 60% or so.

These copolymers having less than 5% of styrene or other cyclicconstituent can also be used as viscosity index improvers in lubricatingoils, diesel fuels or even gasoline.

Another valuable characteristic of this invention is that these newcopolymers lend themselves very peculiarly to the formation of many newchemical derivatives because the very small proportion of styrene orother cyclic constituent combined into the copolymer makes theseproducts susceptible to reaction with strong acids such as sulfuricacid, nitric acid, as well as to other chemical agents such ashalogenation, oxidation, sulfurization, treatment with phosphorussulfides, e. g. P285, alkylation, e. g. with amyl chloride, acylation,e. g. by acetyl chloride, sebacyl chloride, phthalyl chloride, as wellas other interlinking resinifying agents, e. g. formaldehyde, ethylenedichloride, chlorinated paraflin wax, etc.

The invention will be better understood from a consideration of thefollowing experimental data.

EXAMPLE 1 A. copolymerization feed was formulated from 97% by weight ofisobutyl and 3% of styrene. To this mixed feed, powdered solid carbondioxide was added to cool the mixture to 78" C. and then boron fluoridegas was bubbled slowly into the mixture with stirring. Copolymer formedat a very rapid rate. The product had a molecular Weight of about 33,000and the yield was about 47%. The copolymer was soluble in benzene attemperatures as low as 20 0., whereas polybutene of the same molecularweight came out of solution at 20 C.

EXAMPLE 2 80 parts by weight of natural rubber smokedsheet and othercompounding and curing ingredi- -ents as listed herebelow andv thencured at 285-- 287" F. For comparison a composition identical except forthe omission of the isobutylenestyrene copolymer, was similarlycompounded and cured. The abrasion resistance and flex-resistance of theresulting products after curing for various periods from 5 mins. to 20mins. are

also shown herebelow:

Table I 'Reclpe No 1 2 Ingredients:

' Smoked sheet 80 Kosmobilc 66 (carbon black) 50 50 Pine tar 4 4 B. L.E. powder (antioxidant). 1 1 Zinc oxide 5 5 Stearic acid 3. 5 3. 5Captax 1 0.8 0.8 D. P. G. (diphenylguanidine) 0.2 0. 2 Sulfur 3 3Oopolyrner 2 20 Abrasion Resistance (AS'IM D394-40) Mins. cure at285-287" F.:

Flex Resistance to #10 cracking (modif. of ASTM D8l3-44T)Mercaptobenzothiazole.

EXAMPLE 3 Styrene is soluble in a mixture of 1 volume of isobutylene and3 volumes of liquid ethane, to the extent of about 3% by weight. Aseries of tests Table II Accelerator Mol. Wt.

The polymerization temperature was about 88 C.

The above Table II shows that when gaseous boron fluoride alone is usedas catalyst for copolymerizing isobutylene containing about 2.5% byweight of styrene, the resulting copolymer has a molecular weight onlyabout 10,000 to 15,000, whereas when the BF3 is supplemented by the useof 0.1% of ether as accelerator, the molecular weight of the resultingcopolymer ranges from about 35,000 to 50,000. This is a surprisinglygood result considering that the copolymerization was carried out in thepresence of only a hydrocarbon material, namely ethane, as solvent andrefrigerant, because styrene has such a low solubility in aliphatichydrocarbons at low temperature that generally a halogenated hydrocarbonliquid such as methyl chloride has been used heretofore incopolymerizing styrene-isobutylene mixtures containing higher amounts ofstyrene, e. g. to 60% or so.

EXAMPLE 4 Another series of tests was made to determine the optimumamounts of BF3 catalyst and butane diluent, for copolymerizing 1% byweight 0! styrene with 99% of isobutylene using 0.1% of J Table IIISolid CO refii tyrant-0.1? ethyl ether added to olefin feed; active I Ifeed99% l fsobutylene1% styrena] Percent BFa Cater Staudinger lystPercent Butane Diluent MOL WL The above. data in Table III show that.when 0.1% ether activator is. used, copolymers ranging from 75,000 toabout 95,000 mol. wt. are obtained with l to 3% of BFs catalyst andwithout any butane diluent, but copolymers having higher molecularweights in the range of 100,000 to 130,000 are obtained with similarconcentrations of ER; but with 10 to 50% by weight of butane diluent.

EXAMPLE 5 Another series of tests similar to those in Example 4 inregard to the copolymerization of 1% of styrene with 99% of isobutylene,was made to determine the optimum amount of ether activator for the BF:catalyst. These tests were carried out using ethane as refrigerant butno heavier material such as butane as diluent. The use of ethane as aninternal refrigerant maintained a copolymerization temperature of about89 C. The various proportions of ether activator used, ranging from 0 to0.4% by weight based on the weight of polymerization feed, and theamounts of BFa used ranging from 1 to 3% and the molecular weights ofthe resulting copolymers. are shown in the following table:

Table IV [Polymerization of 99% isobutylenel% styrene feed with BF;activated catalyst. Ethane refrigerant (3 vol. ethane per vol. activefeed.)]

Percent Staudingcr BF; Mol. Wt.

Percent ethyl ether in feed The above data in Table IV show that when 1%of styrene is copolymerized with 99% of isobutylene using ethanerefrigerant at 89 C. and using 0.1 to 0.4% of ether activator for theBF: catalyst, copolymers of highest molecular weight were obtained with0.3% of ether activator, and with this concentration of activator, 1% ofBFa gave a copolymer of 165,000 mol. wt., 2% of BFs gave 197,000 and 3%gave 250,000. Using 3% of BFa but no ether activator the molecularweight obtained was only 58,000. Also, it may be noted that the 1%styrene type copolymerization is more sensitive to catalyst activationby ether than are copolymerizations using higher amounts of styrene,such as 20%.

EXAMPLE 6 Copolymers having about 2% of combined styrene and 98%isobutylene, were made having two different average molecular weightranges, one about 12,000 and the other about 78,000. These copolymerswere then blended in several concentrations up to 40% by weight in aparaffin wax havin a melting point of about F. All of these blends werecompletely homogeneous even at temperatures well above the melting pointof the wax, showing good solubility of the copolymers of such lowstyrene content in molten paraflin wax. The refractive index of each of9 these blends was determined at 60 C. and the data were summarized asfollows:

Refr. Index of Blends (at 60 0.) M01. wt. of copolymer EXAMPLE '7 M01.wt. of polymeric product (Staudinger method) Percent styrene in feedSample No.

The above data show that when 1% of styrene is copolymerized withisobutylene the molecular weight of the product is lowered about 40% butlarger amounts of styrene up to 4 or 4.5% only make relatively smallfurther reductions in the molecular weight of the resulting copolymers.On the other hand, the presence of the 1 to 4% Or so of styrene in thecopolymer efiects a great improvement in the stability of the copolymeragainst molecular weight breakdown when subjected either to mechanicalshear, elevated temperature or oxygen.

For instance, the following mill stability tests show that theabove-described copolymers having from 1 to 4.5% of combined styrenesuffer. much lower breakdown in molecular weight than a polybutene madeunder the same polymerization conditions. In this series of tests inwhich the polymer was milled on a pair of steel rolls such as commonlyused for hot milling rubber, the mill clearance used was 0.015 inch andthe mill temperature was 305 F. Samples were taken every mins. up to 1hour.

M ill stability tests [Molecular Weights at different milling times.]

.10 the original molecular weight, whereas the copolymer with even aslittle as 1% of styrene broke down from 138,000 to only 39,000, therebyretaining 28.2% of its original molecular weight. This is a 247%improvement as compared to the 11.4% molecular weight retention of theplain polybutene. Making similar calculations for the other data in theabove table, the relative improvements are tabulated as follows:

Percent im- Percent Percent 221222 1 1 2)?? Percent styrene in feed 01.Wt. g az butene, for retained g each 1% styrene 1n copolymer Thesecalculations on the relative improvements indicate that the greatestproportionate improvement is obtained with the first per cent ofstyrene, and that although subsequent further additions of styrene inthe polymerization feed effect further improvements in the molecularweight retention durin milling, such subsequent additions of styrene arerelatively less effective when compared on the basis of the amount ofstyrene used. It is also significant that as little as 4.5% of styrenein the feed produces about mol. wt. retention, so that obviously muchlarger amounts of styrene such as 20% or 50% could not possibly efiect amuch greater improvement in mol. wt. retention than is obtained withthis still relatively minute amount of 4.5%.

It is believed that these data show that within the range of very smallproportions of styrene. i. e. from 0.5 to 4.5% styrene, the small amountof styrene monomer has two efiects on the polymerization of theisobutylene monomer. One is that it reduces the molecular weight, andthe other is that it affects the molecular weight distribution, tendingto give a narrower spread in the range between the polymer moleculeshaving the highest molecular weight and those of the lowest molecularweight formed under many particular conditions. It is believed that thishelps to account for the improved stability obtained by the copolymersof the low styrene content of this invention.

EXAMPLE 8 4.5% by weight of styrene was copolymerized with 95.5% ofisobutylene at 10l.3 C., using 2 volumes of methyl chloride as solventper volume of active olefin feed, and using as catalyst The above datashow that the plain polybutene broke down from a molecular weight of221,000

A1C13 in CHsCl solution. The yield of the copolymer was 64% (dry weight)and its molecular,

to about 25,000 and thus retained only 11.4% of 75 weight was 82,000 (byStaudinger method). This 1.0% by weight. of m thyl nneth l st rene wascopolymerized with 96% of isobutylene at 101.3 (31, using 2 volumes ofmethyl chloride as solvent per volume of active olefin feed and using ascatalyst AlBrz in QI-hbl solution (1% The yield of the copolymer was 49%solution). (dry wt.) and its molecular weight was 69,000 (Staudingerl.This copolymer had. a. tensile. of 50.lbs-./sq. in. and an elongation of1.840%. fhe polymer, wasv soluble in diisobutylene, benzene, and.toluene.

EXAMPLEJQ A. pol me iza on e d. 3%. y weigh of W- time. an 9 b we ht Qfse ui lene was diluted w t olumes. fli id e onane pe olum o ac ants andpolyme z at .0. c. 5E531)": a as ca a yst h mount oi Fs. use being about0,3'%, on the weight of polymerizaies fee he y e d o co l me s about80%, and ithad an average molecular weight of bout 244100, by thestaudinger method. This product is of value as an adhesive and as a V.I. improver in lubricating oils.

A polymerization feed' was formulated by blending 1 part by weight ofstyrene with 99 parts by weight of isobutylene. To this mixture in aDewar flask was added 1000 grams of'powdined-G02. To this mixture wasadded 150 ml. of catalystsolutioncontaining 0.3 gram AlBrzCl/ 100 ml. orliquidbutane. After the reaction-,. the product was removed, washed, anddried. fhe yield was 33%. The polymer was slightly yellow. Theintrinsicviscosity of the polymer was 0.864, and the molecular weight(Staudinger) was about 21,000: This copolymer was blended in severalconcentrations with a solvent extracted paraflinic lubricating oil basestock and tested for viscosity and V. f. (Viscosity Index)characteristics with; the following results;

6 As the V. I. of the lubricating oil base stocle. was

112, it is apparent that the small additionsof 1- and 3% of thecopolymer effected a very substan,-.

tial increase in the V. I. up to 131 and 137 respec tively.

EXAMPm 12 A cop m o bout by, weiaht styr n and 95% 6f isobutylene wasmade 1;.25 c, in,

methyl-chloride diluent. using as catalyst. a. S lution ofaluminumchloride in methyl chloride.

12 The yield of copolymer was about and the average molecular weight bythe Staudinger method was about 10,435.

This copolymer was then used as plasticizer for a GR-S (75% butadiene,25% styrene) type of synthetic rubber, and tested for various physicalproperties. before and after curing. For comparison, some of theunplasticized synthetic rubher. was also tested. The compounding recipeused was as follows:

Parts/wt. GR-S ZnO 5 Qarbon black (EPC) 1 45 Sulfu 1- Money 0.4Plasticizer 10 Properties before curing Control Plasticized WilliamsPlasticity-Recovery (5 Kg.

at 70 C 108-14.

Mooney at 212 F.,l} 49. Extrusions:

0 Ins/Min 44. 20. Gina/Min 96. 05. Gina/Inch 2. 20 2. l5.

Tac Very s1ight. Fair.

These blends were then cured at 287 F. and were tested for physicalproperties after various curing times from 15 minutes to'60 minutes,with the following results:

' The above data showed that before curing, the new copolymerplasticizer was efficient' as a processing aid and greatly increased theextrusion rate, as well as improving the tack. The tests aitercuring;showed a slight reduction in tensile strength, modulus, and Shorehardness, and a slight increase in elongation in the plasticized'blends. These are satisfactory results for the use of 10% ofplasticizer.

This application is a continuation-in-part of application Serial No.656,148 filed March 21, i946; now- Patent 2,609,359.

It is not intended that this invention be limited to the specificmaterials. which have been mentioned merely for the sake of illustrationbut only by the-appended claims in which it is intended to claim allnovelty inherent in the invention as well as allm'odifications comingwithin. the scope 5 and spirit of the invention.

What is claimed is:

1. The process of preparing substantially saturated; rubber-y copolymers having. an average; molecular. weight above: 30g0'00, whichconsists in copolymerizing about 0.5 to 45% by weight ofi styrene withabout 95.5 to 99.5% of isobutylene inthe presence-of. about 2 to 3volumesof methyl chloride as solvent per. volume of. mixed reactants,and: using, as catalyst a v solution of aluminum. chloride in methylchloride, said process being 13 carried out at a temperature betweenabout -50 C. and 150 C.

2. A product consisting of essentially a rubbery substantially saturatedtwo-component copolymer of more than 95% of isobutylene and at leastabout 0.5% but less than 5% of styrene, said copolymer having an averagemolecular weight of at least 30,000, and being soluble in highlyparaffinic lubricating oils at temperatures as low as 10 C. and beingsoluble in benzene at 20 C.

3. Product according to claim 2 having an av erage molecular weight ofat least 0,000.

4. A two-component product consisting essentially of a copolymer of 97%by weight of isobutylene and 3% of styrene, said copolymer having anaverage molecular weight of about 33,000 and being soluble in benzene attemperatures as low as 20 C.

5. The process which comprises copolymerizing a mixture consistingessentially of at least about 0.5% but less than 5% by weight ofstyrene, with at least 95% by weight of an isoolefin having 4 to 5carbon atoms, there being no aliphatic polyenes present in the reactionmixture, at a temperature below 0 C., with a Friedel- Craft catalyst.

6. Process according to claim 5 carried out in the presence of aFriedel-Craft catalyst promoted by a small amount of an ether.

7. Process according to claim 5 catalyzed by a solution of aluminumchloride in a lower alkyl halide of 1 to 2 carbon atoms.

8. Process according to claim 5 carried out in the presence of 1 to 5volumes of inert solvent per volume of mixed reactants.

9. A product consisting essentially of a copolymer of more than 95% byweight of an isoolefin having 4 to 5 carbon atoms and at least about0.5% butless than 5% by weight of styrene, and having no aliphaticpolyenes copolymerized therein.

10. A product consisting of a copolymer of more than 95% by weight of anisoolefin having 4 to 5 carbon atoms and at least about 0.5% but lessthan 5% by weight of styrene.

WILLIAM J. SPARKS. DAVID W. YOUNG.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,274,749 Smyers Mar. 3, 1942 2,384,916 Holmes Sept. 18, 19452,446,536 Hardy Aug. 10, 1948 2,609,359 Sparks Sept. 2, 1952

2. A PRODUCT CONSISTING OF ESSENTIALLY A RUBBERY SUBSTANTIALLY SATURATED TWO-COMPONENT COPOLYMER OF MORE THAN 95% OF ISOBUTYLENE AND AT LEAST ABOUT 0.5% BUT LESS THAN 5% OF STYRENE, SAID COPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OF AT LEAST 30,000 AND BEING SOLUBLE IN HIGHLY PARAFFINIC LUBRICATING OILS AT TEMPERATURES AS LOW AS 10* C. AND BEING SOLUBLE IN BENZENE AT 20* C. 